Aerial method to mitigate vibration on transmission towers

In December of 1995, during a routine helicopter patrol, it was discovered that the center phase support wing on an "L-Tower" (steel lattice tangent tower) had failed. During restoration and repairs to this tower, and on a subsequent maintenance project, cracks were found in some steel pieces on other towers. Typically, these cracks radiated out from one of the pre-drilled holes on the tip of the wing. Speculation at that time was that the cause of these failures could be attributed to some form(s) of vibration in the steel members of the tower. Using a helicopter and an innovative hell-exit procedure, an intensive inspection program was undertaken to determine the extent of the problem. As a result of these inspections, and in conjunction with research into the cause of the failures, a decision was made to install vibration dampers on the affected towers. Again, a helicopter was utilized to deploy linemen onto the towers. This paper details a brief overview of the research that was required, the inspection of the towers in our system,, and the installation of anti-vibration dampers on the affected members on the towers.